JPH07116511B2 - Manufacturing method of non-oriented electrical steel sheet with excellent magnetic properties - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a non-oriented electrical steel sheet, including iron loss,
It is intended to provide a method capable of manufacturing an electromagnetic steel sheet excellent in magnetic flux density at low cost.

[Prior Art] The so-called low-grade non-oriented electrical steel sheet having a Si content of 1% or less has a high iron loss value, but has a high magnetic flux density and is inexpensive. Therefore, it is mainly used in small motors for home appliances. Has been done.

There are two main magnetic properties required for electromagnetic steel sheets, iron loss and magnetic flux density, and various metallurgical factors that determine these magnetic properties include steel composition, ferrite grain size, and texture. It has been known. Increasing the Si content and increasing the specific resistance is effective for reducing the iron loss, but increasing the ferrite grain size is the most effective for decreasing the iron loss value at a constant Si level. . Further, in order to improve the magnetic flux density, it is necessary to develop a texture that is favorable in terms of magnetic properties. Based on these, in order to improve the magnetic characteristics of the non-oriented electrical steel sheet, conventionally,
The following techniques are disclosed.

Technology for hot-rolled sheet annealing after hot rolling
54-68717) Technology for performing self-annealing by hot rolling and high-temperature winding (for example, JP-A-54-76422) Technology for performing double cold pressure and double annealing (for example, JP-A-60-39)
No. 121) Technology for coarsening the grain size by utilizing AlN precipitation (Japanese Patent Publication No. 50)
(-8976, JP-A-61-136626) Among the various techniques described above, the method of (1) reduces the iron loss by increasing the cold pressure and the ferrite grain size after annealing by annealing at the hot rolled sheet stage. In order to improve the magnetic flux density by improving the texture, the magnetic flux density cannot be avoided because a new annealing process is added.

The method of (1) is a method of performing self-annealing with the heat retained by the hot-rolled sheet after rolling, which is more advantageous in terms of cost. However, in order to obtain the effect by this method, it is necessary to make the coiling temperature extremely high, which makes stable operation difficult and it is difficult to obtain uniform characteristics over the entire length of the coil. Further, there is also a problem that the surface quality is remarkably deteriorated due to internal oxidation during winding.

The method (2) has a larger number of steps than that of the method (2), resulting in a significant increase in cost, and is a manufacturing method that conflicts with the cost reduction, which is the mission of low-grade electrical steel sheets.

In the method of, the pinning effect of fine AlN precipitation is used in reverse, by releasing the pinning of AlN and causing secondary recrystallization during finish annealing, coarse ferrite grains appear, and low This is a technology for reducing iron loss. Of these, Japanese Patent Publication No. 50-8976 contains C in an amount of 0.005 wt% or more,
Although it is intended to facilitate precipitation of AlN during finish annealing, in order to avoid magnetic aging due to C, annealing must be performed in a decarburizing atmosphere, resulting in a large decrease in production efficiency. Further, by using a high C material, a production method for simultaneously performing the contradictory effect of facilitating the precipitation of AlN during finish annealing, while at the same time reducing the carbon content by decarburization. Is. Therefore, since the temperature and time of AlN precipitation do not match the temperature and time of decarburization progress, it is difficult to stabilize the precipitation state of AlN, and it is difficult to stabilize coarsening. Further, since the technique is aimed only at lowering iron loss due to coarsening of ferrite grains, the magnetic flux density, which is another important index of magnetic characteristics, tends to be rather lowered due to coarsening of ferrite grains. In addition, JP 61-
No. 136626 is a technique aimed at promoting precipitation of AlN by adding P and coarsening ferrite grains to reduce iron loss. However, like the above-mentioned technique, this technique is also only aimed at reducing iron loss due to coarsening of ferrite grains, and no consideration is given to improving magnetic flux density. Therefore, the compositional structure of the steel has not been optimized for precipitation of AlN, so that the effect of improving the magnetic flux density, which will be described later, is not observed and is at a low level.

[Problems to be Solved by the Invention] Although the ferrite grain coarsening technique utilizing AlN precipitation described above achieves a low iron loss, the magnetic flux density is not at a satisfactory level. In particular, in the field of small motors targeted by the present invention, if the magnetic flux density is low, further downsizing of the motor cannot be achieved, and it also leads to an increase in current during use. If you do, you will not get a high rating. For this reason, the development of magnetic steel sheets having excellent iron loss and magnetic flux density while waiting for the advantages of low cost has been awaited.

In view of the problems of the conventional method described above, the present invention is to provide a method for manufacturing a non-oriented electrical steel sheet which enables a reduction in iron loss by a low-cost manufacturing method and has a remarkably high magnetic flux density. .

[Means for Solving the Problems] In the production of a low Si non-oriented electrical steel sheet, the present inventors have
We have conducted experiments and research to achieve both low iron loss and high magnetic flux density without increasing costs. As a result, the solid solution state of AlN before finish annealing was optimized by specifying both the steel composition and the heating temperature during hot rolling, and the coiling temperature, and in the subsequent finish annealing, first recrystallization was performed by annealing in the previous stage. It is now possible to improve magnetic properties, especially magnetic flux density, by optimizing the texture and performing continuous annealing by a two-step annealing method in which ferrite grains are coarsened by secondary recrystallization during subsequent high-temperature annealing. The present invention has led to the completion of the present invention.

That is, the feature of the present invention is that C: 0.005 wt% or less, Si: 0.1
~ 1.0wt, Mn: 0.25wt% or more, P: 0.03wt% or more, sol.Al:
0.004 to 0.080 wt%, N: 0.001 to 0.005 wt%, balance Fe and unavoidable impurities, and the atomic weight ratio of sol.Al content and N content is 2 ≦ [sol.Al (at%) / N (at%)] ≤ 15 Slabs with a composition satisfying 15 are heated to 1150 ° C or higher and hot-rolled, then 450 ≤ CT ≤-7.5 {Al (at%) / N (at%)} + 600 (° C ) In the range of a winding temperature CT (° C), the steel strip is pickled, cold-rolled, and then finish-annealed. In the finish-annealing, the heating rate is 5 ° C / sec in the preceding stage, and ( Recrystallization completion temperature -50) ℃ or more, (recrystallization completion tone +100) ℃ or less in the temperature range of 30 seconds or more, followed by subsequent annealing 800
The purpose is to perform a two-stage annealing in which annealing is performed for 1 minute or more at a temperature of ℃ or more.

In the present invention, the recrystallization completion temperature is defined as the temperature at which 100% recrystallization is carried out when the temperature is maintained for 1 minute.

Hereinafter, the configuration of the present invention and the reason for the limitation will be described in detail.

First, the reasons for limiting the component composition of steel will be described.

C: As described later, if C exceeds 0.005 wt%, the texture improving effect due to the interaction between C and Mn cannot be obtained even if other components and processes are optimized, and high magnetic flux density cannot be achieved. Further, if a large amount of C is contained, it is necessary to carry out the finish annealing in a decarburizing atmosphere. In this case, the progress of decarburizing affects the precipitation of AlN, and the precipitation state of AlN itself becomes unstable. Therefore, in order to achieve a high magnetic flux density, stabilize AlN precipitation, and prevent magnetic aging, an ultra-low carbon steel with C: 0.005 wt% or less is used.

An increase in Si: Si has a large effect of increasing the specific resistance and decreasing the iron loss, so the lower limit is made 0.1 wt%. However, 1.0 wt%
If it exceeds, the saturation magnetic flux density will be lowered and the cost will be increased, so the upper limit is made 1.0 wt%.

Mn: In the present invention, Mn is an important component for improving texture. As will be described later, even if the amount of Mn is less than 0.25 wt%, the ferrite grains are coarsened and the iron loss is reduced,
The improvement of recrystallized grain selectivity and texture due to the interaction with C is not achieved, and the magnetic flux density is not improved. Therefore, the lower limit is 0.25 wt%. However, even if Mn is increased excessively, it will only increase the cost. Therefore, it is preferable to add Mn in an upper limit of 2%.

P: Usually, P is often added to improve punchability, but in the present invention, it is defined as an essential component as an element that promotes and stabilizes the precipitation of AlN during finish annealing together with the improvement of punchability. When P is less than 0.03 wt%, even if the solid solution state of AlN before finish annealing is optimized, sufficient A during finish annealing is obtained.
The precipitation amount of lN cannot be obtained, and coarsening of ferrite grains cannot be realized. Therefore, the lower limit is made 0.03 wt%. However, from the viewpoint of preventing the reduction of the rolling property and the punching property due to embrittlement, it is desirable that P is 0.5 wt% or less.
If P is added, the effect of suppressing grain growth is strengthened. Therefore, if this point is also taken into consideration, it is preferable to set 0.3 wt% as the upper limit.

sol.Al: sol.Al is the most important element in the present invention. The present invention utilizes the grain boundary pinning effect and the texture improvement effect due to the precipitation of fine AlN during finish annealing. Therefore, the amount of sol.Al is limited to 0.004 to 0.080 wt% which is suitable for precipitation of fine AlN. If it is less than 0.004 wt%, the required precipitation amount of AlN cannot be obtained. On the other hand, 0.080 wt%
If it exceeds, the pinning effect cannot be utilized because the precipitated AlN aggregates and coarsens.

N: N is also an element that affects the precipitation of AlN. 0.001wt%
If it is less than this, sufficient precipitation of AlN cannot be obtained. On the other hand 0.005wt%
If it exceeds, magnetic properties are deteriorated.

[Sol.Al (at%) / N (at%)]: As described above, Al amount and N amount affect the precipitation of AlN, but the precipitation of AlN is uniquely determined by each content. Not Al
The precipitation amount, size and distribution form of AlN are determined by the abundance ratio of the amount and the amount of N. When the atomic weight ratio [sol.Al (at%) / (at%)] (hereinafter simply referred to as [Al / N]) of the sol.Al amount and the N amount is less than 2, the amount of AlN precipitation required for pinning is obtained. I can't. Further, if [Al / N] exceeds 15, the pinning effect of fine AlN, which is an important factor in the present invention, cannot be utilized because once precipitated AlN aggregates and coarsens even if the hot rolling conditions are optimized. .

Next, the processing and processing conditions of the present invention will be described together with the component conditions.

In the present invention, the steel having the above-described composition is subjected to hot rolling. Regarding the heating temperature during hot rolling, heating at a temperature of 1150 ° C. or higher is essential in order to sufficiently promote the solid solution of AlN. Further, in the present invention, it is an essential condition that the solid solution of AlN is sufficient before finish annealing, and it is intended to realize this at low cost without solution annealing in the hot rolled sheet stage. . For this purpose, not only the heating temperature during hot rolling but also the winding temperature after rolling is controlled within an appropriate range,
Suppressing AlN precipitation during winding is an important point. The following tests were conducted to clarify this point.

The slabs of steels A1 to A8 having different amounts of Al and N as shown in Table 1 were heated to 1250 ° C and hot-rolled, and then wound at a temperature of 450 to 650 ° C. Subsequently, after pickling and cold rolling to a plate thickness of 0.5 mm, the previous stage was heated at a heating rate of 5 ° C / s for 6
Finish annealing was carried out by continuous annealing in a two-stage annealing cycle of 30 ° C. × 1 minute and the subsequent stage at a heating rate of 3 ° C./s at 850 ° C. × 2 minutes. FIG. 1 shows the effects of [Al / N] and winding temperature on the iron loss (W _15/50 ) of these steel sheets.
As is clear from this figure, the good region where the iron loss is less than 5.0 W / kg depends on both [Al / N] and the coiling temperature.
In the region where [Al / N] is less than 2, iron loss of less than 5.0 W / kg has not been achieved at any winding temperature, and conversely when viewed at the same winding temperature, [Al / N] is The iron loss is 5.0 W / kg or more even at a certain level or higher, which is optimal [Al / N]
It turns out that there is a range. The optimum range of this [Al / N] is expanding as the winding temperature decreases. That is,
If [Al / N] is 15 or less, the winding temperature is [-7.5 {Al (a
It has been clarified that the iron loss value of less than 5.0 W / kg can be achieved by controlling the temperature to be t%) / N (at%)} + 600] ° C or less. This phenomenon is due to coarsening of ferrite grains due to fine AlN precipitation and secondary recrystallization. [Al / N] is 2
In the region of less than, even under conditions suitable for solid solution of AlN, such as low temperature winding, coarsening does not occur because the amount of AlN precipitation is small. On the other hand, when [Al / N] is high or the coiling temperature is high, precipitation of AlN occurs, but since AlN aggregates and coarsens, coarsening of ferrite grains does not occur. On the other hand, when [Al / N] and the coiling temperature are in the ranges specified by the present invention, the crystal grains are fine due to pinning of fine AlN in the stage of primary recrystallization, but thereafter the pinning of AlN is When it is weakened and exceeds a certain limit, secondary recrystallization is caused by the grain growth driving force at the time of release, and the ferrite grains are coarsened to achieve a low iron loss.

In the present invention, based on these results, [Al / N] is defined as 2 to 15, and the winding temperature is [-
7.5 {Al / (at%) / N (at%)} + 600] ° C or less.

It should be noted that lowering the winding temperature is effective for suppressing AlN precipitation during winding, but an extremely low winding temperature causes shape defects such as plate thickness variation due to uneven cooling during water cooling. Therefore, the lower limit is limited to 450 ° C.

In order to stably control AlN precipitation in continuous annealing as in the present invention, not only optimization of the solid solution state of AlN,
Furthermore, it is necessary to take measures to accelerate the precipitation of AlN. Therefore, as a result of studying various methods, it became clear that the addition of P was the most effective.

As shown in Table 1, steels B1 to B5 in which [Al / N] is about 4 and the amount of P is changed, and steels [Al / N] are around 11 and in which P amount is changed are C1 to B5.
The slab of C4 was heated to 1250 ° C., hot-rolled, wound at 500 ° C., subsequently pickled and cold pressed to a plate thickness of 0.5 mm. After that, the previous stage was heated at 10 ℃ / s at 630 ℃ × 1.5 minutes,
Continuous annealing was performed by a two-stage annealing cycle in which the latter stage was heated at 830 ° C for 1.5 minutes at a heating rate of 10 ° C / s. FIG. 2 shows the effect of P on the iron loss (W _15/50 ) of the steel sheet thus obtained. According to this, in any [Al / N], when the amount of P is 0.03 wt% or more, secondary recrystallization occurs, and the ferrite grain is coarsened, so that the iron loss is 5.0 wt% or less, which is a good value. . On the other hand, when P is less than 0.03 wt%, the secondary recrystallization does not occur because the precipitation of AlN is insufficient, and only the normal grain growth of the primary recrystallized grains occurs. It is considered that the effect of P on the AlN precipitation is that P reduces the solubility of AlN and promotes the precipitation of AlN.

By controlling the composition of the steel, heating during hot rolling, and the coiling temperature as described above, the solid solution state of AlN before finish annealing is optimized, and by promoting the precipitation of fine AlN by adding P, The iron loss can be reduced by coarsening the ferrite grains. However, as a result of repeated studies on the method of improving not only the core loss but also the magnetic flux density, the inventors have found that
It is an extremely low C material and contains Mn in a certain amount or more, finish annealing is performed by two-step annealing, and by combining the annealing temperature of the first stage and the annealing temperature of the second stage appropriately, it is possible to reduce iron loss and increase the iron loss. This is a new finding that a magnetic flux density can be achieved. The annealing conditions for the two-step annealing, which is the most important manufacturing requirement of the present invention, will be described below.

The slab of steel D shown in Table 2 was heated to 1250 ° C., hot rolled, wound at 520 ° C., pickled and cold rolled to a plate thickness of 0.5 mm. Using this steel sheet, various finish annealings were performed in the two annealing cycles shown in FIGS. 3A and 3B under the conditions of a heating rate of 10 ° C./s and a cooling rate of 5 ° C./s. In FIG.
(A) is a two-stage annealing in which the former annealing is soaked at a temperature of 500 to 850 ° C. for 1 minute, and then the latter annealing is soaked at a temperature of 650 to 900 for 1 minute. (B) is 650-850 for comparison
It is a trapezoidal single-step annealing in which soaking is performed at a temperature of ℃ for 2 minutes.
This is the case where the annealing temperature in the latter stage in (A) is the same as that in the former stage. Fig. 4 shows the magnetic properties of steel sheets that were continuously annealed under each of these finish annealing conditions, first categorized by iron loss (W _15/50 ) of 5 W / kg, and the magnetic flux of steel sheets with an iron loss of less than 5 W / kg. It is classified by density (B ₅₀ ) 1.80T.

First, when comparing the two-step annealing method and the trapezoidal one-step annealing for the iron loss, in the case of the trapezoidal one-step annealing, since the ferrite grains are fine grains at an annealing temperature of 800 ° C or less, the iron loss shows a high value,
By increasing the annealing temperature to as high as 850 ℃, secondary recrystallization occurs and the iron loss value of less than 5W / kg is achieved. On the other hand, when the two-step annealing method is performed and the subsequent annealing is less than 800 ° C, secondary recrystallization does not occur under any conditions. The subsequent annealing is 80
Even if the temperature is 0 ° C or higher, if the annealing temperature in the former stage is as high as 750 ° C or higher, the crystal grains grow to some extent in the stage in the former annealing, so that secondary recrystallization does not occur and the iron loss does not occur. high. However, even in the case of 800 ° C annealing in which the secondary recrystallization did not occur in the trapezoidal one-step annealing method, the secondary recrystallization occurs by performing the two-step annealing by performing the annealing at less than 750 ° C in the previous stage, Iron loss value is less than 5W / kg. in this way,
In the two-step annealing method, the secondary recrystallization is promoted by performing the annealing at a low temperature in the previous step, and it is understood that the two-step annealing method is also effective for promoting the secondary recrystallization.

Next, looking at the behavior of the magnetic flux density in the region where the secondary recrystallization has occurred due to these two-step annealing methods and reduced iron loss, even in the same low iron loss region, there is a difference in the magnetic flux density due to the two-step annealing conditions. Can be seen. As shown in the figure, the magnetic flux density (B ₅₀ ) of 1.80 T or higher is achieved only for the annealing temperature of the latter stage of 800 ° C or higher and the annealing temperature of the former stage in a certain temperature range. The lower limit of this temperature range is almost the same as (recrystallization completion temperature [= 590 ° C] -50) ° C in this test steel, and the upper limit is equivalent to (recrystallization completion temperature +100) ° C. . When the annealing temperature in the former stage is lower than (recrystallization completion temperature −50) ° C. or higher than (recrystallization completion temperature +100) ° C., the magnetic flux density is less than 1.80 T. Further, when the annealing temperature in the trapezoidal one-step annealing is set to the temperature range of the first-stage annealing, or when the temperature range of the second-stage annealing is similarly set, such a high magnetic flux density has not been achieved, and this phenomenon has two stages. It can be seen that this is a phenomenon unique to the two-step annealing that is first realized by performing annealing.

This phenomenon is due to the texture improving effect of AlN precipitation and is presumed to be due to the following reasons. That is, the annealing temperature of the former stage is (recrystallization completion temperature −50) ° C.
In the range of (recrystallization completion temperature +100) ° C, precipitation and recovery of fine AlN and recrystallization compete with each other in the former annealing, and AlN gives selectivity to the nucleation of recrystallization. As a result, it is thought that it affects the formation of recrystallized grain texture, increases the strength of {100} and {110} planes effective for magnetic properties, and suppresses the increase of {111} faces, which is disadvantageous for magnetic properties. . In this way, in the former annealing step, when a fine grain and a large amount of {100} and {110} plane components are formed due to the effect of AlN precipitation and a favorable texture is formed in terms of magnetic properties, the secondary re-annealing during the subsequent high temperature annealing is performed. It is considered that the frequency of occurrence of crystal grains on the {100} and {110} planes also increases in crystals, and the magnetic flux density improves even though they are coarse grains.

On the other hand, when the annealing temperature of the former stage is lower than (recrystallization completion temperature −50) ° C., the precipitation of AlN is small and the recrystallization is insufficient in the annealing of the former stage, so that the texture improvement phenomenon does not occur. Further, in this case, the precipitation of AlN and the progress of recrystallization occur only in the temperature rising process of the post-annealing, and the proper competition between the two as described above does not occur. For this reason, the primary recrystallization proceeds without effective selectivity of the crystal grains, so that the texture is not improved, and after the secondary recrystallization, only a texture similar to a normal trapezoidal one-step annealing cycle is obtained. .

On the contrary, when the annealing temperature in the former stage is high, the progress of recrystallization in the annealing in the former stage is fast, so that the competitive relationship between precipitation of AlN and recrystallization is not optimized, and the selection phenomenon of crystal grains does not occur. Therefore, even in the secondary recrystallization during the subsequent annealing, the {100} plane,
The preferential growth of the {110} plane does not occur and the magnetic flux density is low.

As described above, the finish annealing is performed in two steps, and the annealing temperature in the preceding step is controlled to compete with AlN precipitation and recrystallization to optimize the texture, thereby improving not only the low iron loss but also the high magnetic flux density. Has been found to be achievable. The dependence of the two-step annealing condition on the magnetic flux density depends on other Si content,
The same range was found under the conditions of [Al / N], steel with P content, and other winding temperature conditions, and the optimum range was the same range.

In order to stably produce these high magnetic flux density materials, further detailed investigations were carried out on the relationship between the two-stage annealing condition and the magnetic flux density in finish annealing for various steels, and it was found that the annealing conditions satisfy the range of the present invention. Nevertheless, low levels of magnetic flux density were found in the steel. When the relationship between the chemical composition and the magnetic flux density was examined for these steels, they were affected by both the C content and the Mn content. The C content was kept below a certain amount, and the Mn content was also kept above a certain amount. It became clear that it is necessary to optimize the stage annealing conditions.

Steel E with varying Mn content based on 0.004% C as shown in Table 2
Slabs of 13 kinds of steels, 1 to E5, steels F1 to F4 with varying Mn content based on 0.008% C, and steels G1 to G4 with varying Mn content based on 0.013% C, are heated to 1200 ° C. After hot rolling, 470 ℃
It was rolled up, and then it was pickled and cold-pressed into a 0.5 mm thick steel plate. The recrystallization temperature of each steel sheet was within the range of 590 ° C to 620 ° C. These steel sheets were heated at a heating rate of 5 ° C./s, and finish annealing was performed by two-stage annealing in which the former stage was 640 × 1.5 minutes and the latter stage was 840 ° C. × 2 minutes. FIG. 5 shows the effect of Mn content and C content on the magnetic flux density (B ₅₀ ) after finish annealing. As shown in the figure, when the C content is high such as 0.008% C material and 0.013% C material, the magnetic flux density is as low as about 1.75 at any Mn content. Even when the C content is low, such as 0.004% C material, when the Mn content is less than 0.25 wt%, it is at a level equivalent to or slightly inferior to the high C material, and Mn is 0.25 wt%.
%, The magnetic flux density shows an excellent characteristic value of 1.78 or more. Thus, it can be seen that the high magnetic flux density is achieved only under the conditions of low C and high Mn.

Although the detailed mechanism of the effect of improving the magnetic flux density by C and Mn is not clear, it is considered as follows. That is, under the condition of extremely low C, coexistence of Mn in a certain amount or more causes C and Mn to appropriately interact with each other, which affects the selective action of the recrystallization orientation by AlN. As a result {10
It seems that a texture with preferential growth of the 0} and {110} planes will be obtained. In the high C material, the magnetic flux density is not improved even if the Mn is increased, but this is because the interaction with Mn becomes too strong and adversely affects the selectivity, or C changes the AlN precipitation timing itself. Therefore, it is considered that it does not compete with recrystallization appropriately.

As described above, low iron loss and high magnetic flux density can be obtained by incorporating Mn in a certain amount or more in the ultra-low C material, by performing the finishing annealing in two stages, and by utilizing the AlN precipitation control and the recrystallization orientation selection effect of AlN. It became clear that it is possible to achieve both.

Therefore, in the present invention, C is 0.005 wt% or less, Mn
With respect to, 0.25 wt% or more is specified as the condition. For more stable and higher magnetic flux density, the Mn content should be 0.50wt%
The above is preferable. Regarding the finish annealing conditions, the annealing temperature in the first stage of the two-stage annealing is set in the range of (recrystallization completion temperature −50) ° C. or higher and (recrystallization completion temperature +100) ° C. or less, which has a large effect of improving the magnetic flux density, and the annealing temperature of the latter stage Is defined as 800 ° C or higher at which secondary recrystallization occurs. The annealing temperature in the latter stage is 950 ° C because the energy cost increases if it exceeds 950 ° C.
The following are preferred. In the present invention, AlN is precipitated during the former annealing. Therefore, the heating rate during the pre-annealing is specified to be 5 ° C./s or more to prevent the precipitation of fine AlN during the temperature rising process. The heating rate in the post-annealing is not specified because it does not significantly affect the progress of secondary recrystallization, but since this manufacturing method presupposes continuous annealing, it is substantially 1 ° C.
/ s or more. Next, the heating time in the first-stage annealing is set to 30 seconds or more to secure the required amount of precipitation and recrystallization of fine AlN even at the lower limit annealing temperature of the present invention, and the soaking time in the second-stage annealing is the secondary re-heating. It should be 1 minute or longer for the progress of crystallization. The upper limit of the soaking time is preferably 10 minutes or less in terms of production efficiency.

Magnetic steel sheet according to the method of the present invention, even if assembled into a product as it is after punching by a customer, exhibits very excellent characteristics, but after being punched, it is subjected to strain relief annealing,
After that, there is no problem when assembled into a product, and it exhibits superior characteristics.

〔Example〕

The slabs having the eight kinds of compositions shown in Table 3 were hot-rolled under the hot-rolling conditions shown in Table 4, followed by pickling and cold-rolling to obtain a steel plate having a thickness of 0.5 mm. Two-step annealing was performed on these steel sheets under the finish annealing conditions shown in Table 4. In addition,
The soaking time was fixed at 1 minute for the first stage annealing and 2 minutes for the second stage annealing. In the right column of Table 4, the iron loss (W
_15/50 ) and magnetic flux density (B ₅₀ ) are shown. As is clear from the table, the steel sheet produced under the components of the present invention, the heating temperature, the coiling temperature, and the two-step annealing condition shows very excellent iron loss and magnetic flux density balance. Especially regarding the magnetic flux density
Achieved 1.81 or more for 0.19% Si material (steel type J) and 1.79 or more for 0.82% Si material (steel type L). On the other hand, when the component, heating temperature, or coiling temperature is out of the range of the present invention, secondary recrystallization does not occur, and thus iron loss is high. When the annealing conditions of the two-step annealing are out of the range of the present invention, the magnetic flux density is low even if the iron loss is reduced to some extent.

[Effects of the Invention] As described above, according to the method of the present invention, in the production of a non-oriented electrical steel sheet, without using means for increasing costs such as hot-rolled sheet annealing, double cold pressing, and double annealing, Further, it is possible to provide a magnetic steel sheet having a high production efficiency and a very excellent iron loss and magnetic flux density without deteriorating the product characteristics such as the deterioration of the surface properties, and the industrial effect thereof is extremely large.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of [Al / N] and winding temperature on iron loss after finish annealing. FIG. 2 is a graph showing the effect of [Al / N] and P on iron loss after finish annealing. FIG. 3 is an explanatory view showing a heat cycle in finish annealing. FIG. 4 is a graph showing the effect of finish annealing conditions on iron loss and magnetic flux density. FIG. 5 is a graph showing the effect of C and Mn on the magnetic flux density.

Claims (1)

[Claims] 1. C: 0.005 wt% or less, Si: 0.1-1.0 wt%, Mn:
0.25wt% or more, P: 0.03wt% or more, sol.Al:0.004-0.080w
t%, N: 0.001 to 0.005 wt%, balance Fe and unavoidable impurities, and the atomic weight ratio of sol.Al content and N content is 2 ≦ [sol.Al (at%) / N (at %)] ≦ 15, slabs with a composition satisfying 15 are heated to over 1150 ° C and hot-rolled, and then 450 ≦ CT ≦ −7.5 {Al (at%) / N (at%)} + 600 (° C) At a coiling temperature CT (° C) of the steel strip, the steel strip is pickled, cold-rolled, and then finish-annealed. In the finish-annealing, the heating rate was 5 ° C / sec or more in the preceding stage, and (recrystallization Annealing is performed for 30 seconds or more in the temperature range of completion temperature −50) ° C. or higher and (recrystallization completion temperature +100) ° C. or lower, followed by subsequent annealing.
A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, which comprises performing a two-step annealing in which the annealing is performed at a temperature of 800 ° C or more for 1 minute or more.